Method of recycling silicon component for plasma etching apparatus and silicon component for plasma etching apparatus

ABSTRACT

A method of recycling a silicon component for a plasma etching apparatus includes a collecting process of collecting silicon wastes from any one of a silicon component for a plasma etching apparatus and a silicon ingot for a semiconductor wafer; a measurement process of obtaining a content of impurity based on an electric characteristic of the collected silicon wastes; an input amount determination process of determining an input amount of the silicon wastes, an input amount of a silicon source material, and an input amount of impurity based on the content of impurity obtained in the measurement process and a target value of an electric characteristic of a final product; and a silicon ingot manufacturing process of manufacturing a silicon ingot by inputting the silicon wastes, the silicon source material, and the impurity based on the input amounts determined in the input amount determination process into a crucible.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Patent Application No.2009-221793 filed on Sep. 28, 2009 and U.S. Provisional Application Ser.No. 61/252,205 filed on Oct. 16, 2009, the entire disclosures of whichare incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure relates to a method of recycling a siliconcomponent for a plasma etching apparatus and a silicon component for aplasma etching apparatus.

BACKGROUND OF THE INVENTION

Conventionally, by way of example, in the manufacturing field of asemiconductor device, there has been used a plasma etching apparatus forperforming a predetermined plasma process such as an etching processonto a semiconductor wafer or a glass substrate for a liquid crystaldisplay.

In the plasma etching apparatus, various silicon components have beenused for performing a process onto a semiconductor wafer made of siliconor various silicon films. By way of example, conventionally, in theplasma etching apparatus, there has been used a silicon focus ring as afocus ring installed to surround a semiconductor wafer mounted on amounting table. Further, as an electrode plate of a facing electrodeinstalled to face the mounting table, there has been used a siliconelectrode plate.

In the plasma etching apparatus, when a silicon component such as asilicon focus ring is exposed to the plasma, it is gradually eroded anddegraded and its shape becomes changed. For this reason, reproducibilityof a process becomes worse and if it is continuously used, the processquality would be deviated from an expected management value. Therefore,when the silicon component is eroded and degraded to some extent, it isregarded as an unusable component and discarded as industrial wastes.However, such a silicon component for the plasma etching apparatus ishigh-priced, which causes an increase in cost of consumables (COC)required for running the plasma etching apparatus.

As a countermeasure to this, there has been suggested a method in whicha first ring and a second ring obtained by machining used silicon focusrings are combined and the combined silicon focus ring having a shapecompatibility with a non-used silicon focus ring is recycled (see, forexample, Patent Document 1). However, the method of combining ringsobtained by a machining process is limited to a method of combining themachined rings having the same electric characteristic and the sameshape as the non-used silicon focus ring, and, thus, a recyclablecomponent is very restricted.

By way of example, in the manufacturing field of a solar cell, there hasbeen suggested a recycling method that performs: a process for removingan anti-reflection film and a rear surface silver electrode film from asilicon wafer including a defective solar cell by using a hydrofluoricacid; a process for removing an aluminum electrode layer by using ahydrochloric acid; and a process for removing an impurity layer by usinga mixed liquid of nitric acid and hydrofluoric acid or a sodiumhydroxide in order to recover the silicon wafer including the defectivesolar cell to a silicon wafer capable of forming a silicon solar cellagain (see, for example, Patent Document 2). However, the method ofrecycling the silicon wafer including the defective solar cell cannot beapplied to a method of recycling various used silicon components for aplasma etching apparatus.

Patent Document 1: Japanese Patent Laid-open Publication No. 2004-79983

Patent Document 2: Japanese Patent Laid-open Publication No. 2005-166814

As described above, in a plasma etching apparatus, the silicon componentfor the plasma etching apparatus is a cause of an increase in cost ofconsumables. Further, conventionally, there has been no effective way ofrecycling various used silicon components for a plasma etchingapparatus, which causes an increase in an amount of industrial wastes.

The present disclosure has been conceived in view of the foregoingconventional circumstances and provides a method of recycling a siliconcomponent for a plasma etching apparatus and a silicon component for aplasma etching apparatus capable of reducing cost of consumables of theplasma etching apparatus, reducing an amount of industrial wastes, andpromoting effective use of resources as compared with the conventionalones.

BRIEF SUMMARY OF THE INVENTION

In accordance with one aspect of the present disclosure, there isprovided a method of recycling a silicon component in a processingchamber of a plasma etching apparatus performing an etching process on asubstrate. The method includes a collecting process of collectingsilicon wastes from any one of a silicon component for a plasma etchingapparatus and a silicon ingot for a semiconductor wafer; a measurementprocess of obtaining a content of impurity based on an electriccharacteristic of the collected silicon wastes; an input amountdetermination process of determining an input amount of the siliconwastes, an input amount of a silicon source material, and an inputamount of impurity based on the content of impurity obtained in themeasurement process and a target value of an electric characteristic ofa final product; and a silicon ingot manufacturing process ofmanufacturing a silicon ingot by inputting the silicon wastes, thesilicon source material, and the impurity based on the input amountsdetermined in the input amount determination process into a crucible.

In accordance with another aspect of the present disclosure, there isprovided a silicon component in a processing chamber of a plasma etchingapparatus performing an etching process on a substrate. The siliconcomponent contains recycled silicon obtained by a silicon componentrecycling method. The recycling method includes a collecting process ofcollecting silicon wastes from any one of a silicon component for aplasma etching apparatus and a silicon ingot for a semiconductor wafer;a measurement process of obtaining a content of impurity based on anelectric characteristic of the collected silicon wastes; an input amountdetermination process of determining an input amount of the siliconwastes, an input amount of a silicon source material, and an inputamount of impurity based on the content of impurity obtained in themeasurement process and a target value of an electric characteristic ofa final product; and a silicon ingot manufacturing process ofmanufacturing a silicon ingot by inputting the silicon wastes, thesilicon source material, and the impurity based on the input amountsdetermined in the input amount determination process into a crucible.

In accordance with the present disclosure, it is possible to provide amethod of recycling a silicon component for a plasma etching apparatusand a silicon component for a plasma etching apparatus capable ofreducing cost of consumables of the plasma etching apparatus, reducingan amount of industrial wastes, and promoting effective use of resourcesas compared with the conventional ones.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments will be described inconjunction with the accompanying drawings.

Understanding that these drawings depict only several embodiments inaccordance with the disclosure and are, therefore, not to be intended tolimit its scope, the disclosure will be described with specificity anddetail through use of the accompanying drawings, in which:

FIG. 1 is a flowchart showing a process of recycling a silicon componentfor a plasma etching apparatus in accordance with an embodiment of thepresent disclosure; and

FIG. 2 is a longitudinal cross sectional view schematically showing aconfiguration example of a plasma etching apparatus.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present disclosure will be explained indetail with reference to accompanying drawings. FIG. 1 is a flowchartshowing a process of recycling a silicon component for a plasma etchingapparatus in accordance with the present embodiment and FIG. 2 is alongitudinal cross sectional view schematically showing a configurationexample of a plasma etching apparatus.

Referring to FIG. 2, there will be explained a configuration of a plasmaetching apparatus. A plasma etching apparatus 1 is configured as anetching apparatus of a capacitively coupled parallel plate type in whichelectrode plates face each other in parallel and a power supply forgenerating plasma is connected thereto.

The plasma etching apparatus 1 includes a cylindrical processing chamber2 made of an aluminum whose surface is anodically oxidized, and theprocessing chamber 2 is grounded. Further, a substantially cylindricalsusceptor support 4 for mounting thereon a target object such as asemiconductor wafer W is installed in a bottom portion of the processingchamber 2, with an insulating plate 3 made of, e.g., ceramictherebetween. Further, a susceptor (mounting table) 5 serving as a lowerelectrode is installed on the susceptor support 4. The susceptor 5 isconnected to a high pass filter (HPF) 6.

Inside the susceptor support 4, a coolant reservoir 7 is provided. Acoolant is introduced into the coolant reservoir 7 through a coolantintroduction line 8 and circulated therein, and discharged through acoolant discharge line 9. A cold heat of the coolant is thermallytransferred to the semiconductor wafer W via the susceptor 5 and thusthe temperature of the semiconductor wafer W is controlled as desired.

An upper central portion of the susceptor 5 is formed in a protrudedcircular plate shape on which a circular electrostatic chuck 11 havingsubstantially the same diameter as the semiconductor wafer W isinstalled. The electrostatic chuck 11 includes an electrode 12 within aninsulating member. Further, a DC voltage of, e.g., about 1.5 kV isapplied to the electrostatic chuck 11 from a DC power supply 13connected to the electrode 12, so that the semiconductor wafer W iselectrostatically attracted by, e.g., a Coulomb force.

A gas passage 14 for supplying a heat transfer medium (for example, a Hegas) to a rear surface of the semiconductor wafer W is formed throughthe insulating plate 3, the susceptor support 4, the susceptor 5, andthe electrostatic chuck 11. Through the heat transfer medium, a coldheat of the susceptor 5 is transferred to the semiconductor wafer W tomaintain the temperature of the semiconductor wafer W at a predeterminedlevel.

An annular focus ring 15 is installed at an upper peripheral portion ofthe susceptor 5 so as to surround the semiconductor wafer W mounted onthe electrostatic chuck 11. The focus ring 15 is made of a conductivematerial and improves etching uniformity. In the plasma etchingapparatus 1, the focus ring 15 is made of silicon and this silicon focusring 15 is one of components for the plasma etching apparatus to which arecycling method of the present embodiment can be applied.

Above the susceptor 5, there is installed an upper electrode 21 facingthe susceptor 5 in parallel. The upper electrode 21 is supported at anupper portion of the processing chamber 2 via an insulating member 22.The upper electrode 21 is composed of an electrode plate 24 and anelectrode support 25 made of a conductive material, for supporting theelectrode plate 24. The electrode plate 24 has a plurality of dischargeholes 23 and faces the susceptor 5. In the plasma etching apparatus 1,the electrode plate 24 is made of silicon and this silicon electrodeplate 24 is one of components for the plasma etching apparatus to whicha recycling method of the present embodiment can be applied.

There is installed a gas introduction port 26 at the center of theelectrode support 25 of the upper electrode 21, and the gas introductionport 26 is connected to a gas supply pipe 27. Further, the gas supplypipe 27 is connected to a processing gas supply source 30 via a valve 28and a mass flow controller 29. The processing gas supply source 30supplies an etching gas used for plasma etching.

There is installed an exhaust pipe 31 at a bottom portion of theprocessing chamber 2, and the exhaust pipe 31 is connected to a gasexhaust unit 35. The gas exhaust unit 35 includes a vacuum pump such asa turbo-molecular pump and is configured to evacuate the inside of theprocessing chamber 2 to be in a predetermined depressurized atmosphere,i.e., to a predetermined pressure of, e.g., about 1 Pa or less. Further,a gate valve 32 is provided at a sidewall of the processing chamber 2,and with the gate valve 32 open, the semiconductor wafer W istransferred to/from an adjacent load-lock chamber (not illustrated).

The upper electrode 21 is connected to a first high frequency powersupply 40, and a matching unit 41 is provided on a power supply linethereof. Further, the upper electrode 21 is connected to a low passfilter (LPF) 42. The first high frequency power supply 40 has afrequency ranging from about 27 MHz to about 150 MHz. Accordingly, it ispossible to generate high-density plasma in a desirable dissociatedstate within the processing chamber 2 by applying a high frequency powerin such a frequency range.

The susceptor 5 serving as a lower electrode is connected to a secondhigh frequency power supply 50, and a matching unit 51 is provided on apower supply line thereof. The second high frequency power supply 50 hasa frequency in a range lower than the frequency of the first highfrequency power supply 40. By applying a high frequency power in such afrequency range, it is possible to provide an appropriate ion actionwithout damaging the semiconductor wafer W serving as a targetsubstrate. It is desirable for the second high frequency power supply 50to have a frequency ranging from about 1 MHz to about 20 MHz, forexample.

As illustrated in FIG. 2, the whole operations of the above-describedplasma etching apparatus 1 are controlled by a controller 60. Thecontroller 60 includes a process control unit 61 having a CPU, forcontrolling each component of the plasma etching apparatus 1, a userinterface 62, and a storage unit 63.

The user interface 62 includes a keyboard through which a processmanager inputs commands to manage the plasma etching apparatus 1 and adisplay for visually showing an operation status of the plasma etchingapparatus 1.

The storage unit 63 stores a control program (software) for executingvarious processes performed in the plasma etching apparatus 1 under thecontrol of the process control unit 61; or recipes that store processingcondition data. If necessary, a required process is performed in theplasma etching apparatus 1 under the control of the process control unit61 by retrieving a necessary recipe from the storage unit 63 in responseto an instruction from the user interface 62 and executing the recipe bythe process control unit 61. Further, the control program or the recipeof the processing condition data which is stored in a computer-readablestorage medium (for example, a hard disk, a CD, a flexible disk, asemiconductor memory or the like) may be used. The control program orthe recipe can be also used on-line by receiving it from anotherapparatus through, for example, a dedicated line whenever necessary.

In case that the semiconductor wafer W is plasma etched by theabove-described plasma etching apparatus 1, the gate valve 32 is opened,and, then, the semiconductor wafer W is loaded into the processingchamber 2 from a non-illustrated load-lock chamber and mounted on theelectrostatic chuck 11. Then, a DC voltage is applied from the DC powersupply 13, so that the semiconductor wafer W is electrostaticallyattracted onto the electrostatic chuck 11. Subsequently, the gate valve32 is closed and the inside of the processing chamber 2 is evacuated toa predetermined vacuum level by the gas exhaust unit 35.

Thereafter, the valve 28 is opened, and a predetermined etching gas isintroduced from the processing gas supply source 30 into a hollow regionof the upper electrode 21 through the processing gas supply pipe 27 andthe gas introduction port 26 while its flow rate is controlled by themass flow controller 29. Then, the gas is uniformly discharged towardthe semiconductor wafer W through the discharge holes 23 of theelectrode plate 24 as indicated by arrows of FIG. 2.

The internal pressure of the processing chamber 2 is maintained at apredetermined level. Then, a high frequency power with a predeterminedfrequency is applied from the first high frequency power supply 40 tothe upper electrode 21. Accordingly, a high frequency electric field isgenerated between the upper electrode 21 and the susceptor 5 serving asthe lower electrode, and thus the etching gas is dissociated and excitedinto plasma.

Meanwhile, a high frequency power with a lower frequency than theabove-described frequency of the first high frequency power supply 40 isapplied from the second high frequency power supply 50 to the susceptor5 serving as the lower electrode. Accordingly, ions in the plasma areattracted toward the susceptor 5 and etching anisotropy is increased byion-assist. During this plasma etching process, silicon components forthe plasma etching apparatus such as the above-described focus ring 15and electrode plate 24 are exposed to the plasma and gradually erodedand degraded. After a predetermined time period, the used siliconcomponents for the plasma etching apparatus are replaced with new onesand, conventionally, they have been discarded as industrial wastes.

When the plasma etching process is ended, the supplies of the highfrequency power and the processing gas are stopped. In reverse order tothe order described above, the semiconductor wafer W is unloaded fromthe processing chamber 2.

Hereinafter, there will be explained a method of recycling siliconcomponents for the plasma etching apparatus such as the above-describedfocus ring 15 and electrode plate 24. In the method of recycling thesilicon components for the plasma etching apparatus, the used focus ring15 and the used electrode plate 24 can be used as silicon wastes.

By way of example, it may be possible to use silicon wastes collectedduring a manufacturing process of silicon components for a plasmaetching apparatus. The silicon wastes may include, for example, acomponent with damage such as a crack or a defect during themanufacturing process, a component having an irregular size, and acomponent having an irregular electric characteristic such as abnormalresistance. Further, it may be possible to use silicon wastes collectedfrom a machining process. The silicon wastes may include, for example,an inner circular residue remaining after the focus ring 15 is cut away.Moreover, it may possible to use silicon wastes such as a cone-shapedlower end and upper end of a silicon ingot, which can be obtained duringa manufacturing process of the silicon ingot.

In the present embodiment, there will be explained a case of usingsilicon wastes originated from the used focus ring 15, the usedelectrode plate 24 or the like among the above-described silicon wastes.In the present embodiment, as shown in the flowchart of FIG. 1, siliconwastes are collected from a silicon component for a plasma etchingapparatus such as the used focus ring 15, the used electrode plate 24 orthe like (step 1).

Then, there is performed a reaction product removal process (step 2) forremoving a reaction product adhered to a surface of the collectedsilicon wastes. In this reaction product removal process, there may beperformed a method of physically removing a reaction product byinjecting a cleaning material and a compressed gas to the siliconwastes. In this case, the cleaning material may be at least one of, forexample, CO₂ particles, Al₂O₃ particles, SiO₂ particles, and nylonbeads.

Further, in the reaction product removal process, it may be possible touse a method of removing a reaction product from the silicon wastes byacid etching or alkali etching instead of or in addition to theabove-described removing method. In this case, the reaction product ischemically removed such that the silicon wastes reach a bulk level.

Further, if the silicon wastes are not originated from the used siliconcomponent for the plasma etching apparatus but collected during amanufacturing process of the silicon component for the plasma etchingapparatus and a reaction product is not adhered thereto, the reactionproduct removal process can be omitted.

Subsequently, there are performed a measurement process of measuring anelectric characteristic (e.g., electrical resistance in the presentembodiment) and mass of the silicon wastes from which the reactionproduct has been removed and a measurement process of measuring acontent of impurity such as boron in the silicon wastes (step 3). Thesilicon components for the plasma etching apparatus may have differentelectric characteristics (e.g., electrical resistance) to meet aproperty requirement for each component. For this reason, when an ingotis manufactured, a predetermined amount of impurity such as boron isadded depending on electrical resistance required for each siliconcomponent for the plasma etching apparatus. In the measurement process,the impurity content is obtained by measuring the electrical resistanceby means of a 4 probe measurement instrument and measuring the mass bymeans of a precise measurement instrument. In order to measure theelectrical resistance, for example, a 4 probe measurement instrumentproduced by Napson Corporation may be employed.

Then, there is performed an input amount determination process (step 4)for determining an input amount of the silicon wastes, an input amountof a silicon source material, and an input amount of impurity based onthe impurity content obtained in the measurement process and a targetvalue of an electric characteristic (electrical resistance in thepresent embodiment) of a final product.

As described above, the silicon components for the plasma etchingapparatus may have different electric characteristics such as electricalresistance to meet a property requirement for each component. By way ofexample, as for a silicon focus ring, an electrical resistance targetvalue may be about 2Ω, and as for a silicon electrode plate, anelectrical resistance target value may be about 75Ω. Based on theseelectrical resistance target values, the total input amount of siliconand the input amount of impurity are determined. Therefore, the inputamount of the silicon wastes, the input amount of the silicon sourcematerial, and the input amount of the impurity are determined based onthe mass of the silicon wastes and the impurity content. If the amountof the silicon wastes is enough to meet the required amount of silicon,the input amount of the silicon source material may be zero. Further, ifthe amount of impurity contained in the silicon wastes is enough to meetthe required amount of impurity, the input amount of the impurity may bezero. Furthermore, as the silicon source material, it may be possible touse a poly-crystalline-silicon or an impurity-containingsingle-crystalline-silicon obtained by adding impurity into asingle-crystalline-silicon and then growing thesingle-crystalline-silicon.

Thereafter, there is performed a silicon ingot manufacturing process(step 5) of manufacturing a silicon ingot by inputting the siliconwastes, the silicon source material, and the impurity into a cruciblebased on the input amounts determined in the input amount determinationprocess and melting them. In the silicon ingot manufacturing process,well-known methods such as a CZ method and a MCZ method may beperformed. Further, by performing a machining process to form thesilicon ingot manufactured in this process into a predetermined shape, anew silicon component for a plasma etching apparatus such as a siliconfocus ring or a silicon electrode plate can be manufactured.

As described above, in the present embodiment, a new silicon componentfor a plasma etching apparatus can be manufactured by recycling a usedsilicon component for a plasma etching apparatus which hasconventionally been discarded as industrial wastes. Therefore, it ispossible to reduce cost of consumables of the plasma etching apparatus,reduce an amount of industrial wastes, and promote effective use ofresources as compared with the conventional ones.

Although there has been explained the embodiment of the presentdisclosure, the present disclosure is not limited to the above-describedembodiment and can be changed and modified in various ways. By way ofexample, there has been explained a case where a silicon focus ring anda silicon electrode plate are illustrated as a silicon component for aplasma etching apparatus, but the same method can be applied to othersilicon components for a plasma etching apparatus. Further, in theabove-described embodiment, a content of impurity is obtained bymeasuring electrical resistance and mass but can be obtained bymeasuring other electric characteristics.

1. A method of recycling a silicon component in a processing chamber ofa plasma etching apparatus performing an etching process on a substrate,the method comprising: a collecting process of collecting silicon wastesfrom any one of a silicon component for a plasma etching apparatus and asilicon ingot for a semiconductor wafer; a measurement process ofobtaining a content of impurity based on an electric characteristic ofthe collected silicon wastes; an input amount determination process ofdetermining an input amount of the silicon wastes, an input amount of asilicon source material, and an input amount of impurity based on thecontent of impurity obtained in the measurement process and a targetvalue of an electric characteristic of a final product; and a siliconingot manufacturing process of manufacturing a silicon ingot byinputting the silicon wastes, the silicon source material, and theimpurity based on the input amounts determined in the input amountdetermination process into a crucible.
 2. The method of claim 1, furthercomprising: a reaction product removal process of removing a reactionproduct adhered to a surface of the silicon wastes.
 3. The method ofclaim 2, wherein the reaction product removal process includesphysically removing the reaction product by injecting a cleaningmaterial and a compressed gas to the silicon wastes.
 4. The method ofclaim 2, wherein the cleaning material includes at least one of CO₂particles, Al₂O₃ particles, SiO₂ particles, and nylon beads.
 5. Themethod of claim 2, wherein the reaction product removal process includesremoving the reaction product of the silicon wastes by acid etching oralkali etching.
 6. A silicon component in a processing chamber of aplasma etching apparatus performing an etching process on a substrate,the silicon component containing recycled silicon obtained by a siliconcomponent recycling method, wherein the recycling method includes: acollecting process of collecting silicon wastes from any one of asilicon component for a plasma etching apparatus and a silicon ingot fora semiconductor wafer; a measurement process of obtaining a content ofimpurity based on an electric characteristic of the collected siliconwastes; an input amount determination process of determining an inputamount of the silicon wastes, an input amount of a silicon sourcematerial, and an input amount of impurity based on the content ofimpurity obtained in the measurement process and a target value of anelectric characteristic of a final product; and a silicon ingotmanufacturing process of manufacturing a silicon ingot by inputting thesilicon wastes, the silicon source material, and the impurity based onthe input amounts determined in the input amount determination processinto a crucible.